The present invention relates to a device for the optical identification of a coding on a diagnostic test strip in an evaluation device in which the test strip is positively movable relative to a reading device for the coding, with a source of light as a transmitter and a light-sensitive element as a receiver.
A device of this kind is known from U.S. Pat. No. 3,907,503 in which the coding consists of a code block applied to a transparent test strip. In the case of this known device, the coding consists of the distance between this code block and the first adjacent test field of the test strip. For the measurement, the test strip is positively guided between a source of light and a photoreceiver. The light emitted from the source of light is received by the photoreceiver through the test strip. In the case of a uniform movement of the test strip, the time gap between the interruption of the light beam by the code block and by the first test field can be used as a coding for certain information. In the present case, various types of strips differ by the distances between code field and the first test field and by the position of the code field on the test strip.
The known device can certainly be used for reading off very simple information from test strips. However, it would be desirable if more information could be accommodated in the test strip and, for example in the case of the introduction of the test strip into the evaluation device, could be transmitted to its electronic memory.
For the accommodation of a greater amount of information, there is, on the other hand, only a very small space available for the test strip. This leads to a correspondingly high information density with corresponding problems with regard to certainty and lack of disturbance of the transmission.